fixes

Author: maximyurchuk

ydb/tests/compatibility/test_rolling.py

@@ -106,7 +106,7 @@ def test_log(self, store_type):
         )
         yatest.common.execute(init_command, wait=True, stdout=self.output_f, stderr=self.output_f)
         run = yatest.common.execute(run_command, wait=False, stdout=self.output_f, stderr=self.output_f)
-        
+
         for _ in self.roll():
             time.sleep(5)
 

ydb/tests/library/compatibility/fixtures.py

@@ -138,8 +138,18 @@ def setup_cluster(self, **kwargs):
         self.cluster.stop()
 
     def roll(self):
+        # from old to new
         for node_id, node in self.cluster.nodes.items():
             node.stop()
             node.binary_path = current_binary_path
             node.start()
             yield
+
+        # from new to old
+        for node_id, node in self.cluster.nodes.items():
+            node.stop()
+            node.binary_path = last_stable_binary_path
+            node.start()
+            yield
+
+        yield